/*
 *  Copyright 2019-2020 Zheng Jie
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package com.wdb.utils;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
import javax.crypto.spec.IvParameterSpec;
import java.nio.charset.StandardCharsets;

/**
 * 加密
 *
 * @author Zheng Jie
 * @date 2018-11-23
 */
public class EncryptUtils {

  private static final String STR_PARAM = "Passw0rd";

  private static Cipher cipher;

  private static final IvParameterSpec IV =
      new IvParameterSpec(STR_PARAM.getBytes(StandardCharsets.UTF_8));

  private static DESKeySpec getDesKeySpec(String source) throws Exception {
    if (source == null || source.length() == 0) {
      return null;
    }
    cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
    String strKey = "Passw0rd";
    return new DESKeySpec(strKey.getBytes(StandardCharsets.UTF_8));
  }

  /** 对称加密 */
  public static String desEncrypt(String source) throws Exception {
    DESKeySpec desKeySpec = getDesKeySpec(source);
    SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
    SecretKey secretKey = keyFactory.generateSecret(desKeySpec);
    cipher.init(Cipher.ENCRYPT_MODE, secretKey, IV);
    return byte2hex(cipher.doFinal(source.getBytes(StandardCharsets.UTF_8))).toUpperCase();
  }

  /** 对称解密 */
  public static String desDecrypt(String source) throws Exception {
    byte[] src = hex2byte(source.getBytes(StandardCharsets.UTF_8));
    DESKeySpec desKeySpec = getDesKeySpec(source);
    SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
    SecretKey secretKey = keyFactory.generateSecret(desKeySpec);
    cipher.init(Cipher.DECRYPT_MODE, secretKey, IV);
    byte[] retByte = cipher.doFinal(src);
    return new String(retByte);
  }

  private static String byte2hex(byte[] inStr) {
    String stmp;
    StringBuilder out = new StringBuilder(inStr.length * 2);
    for (byte b : inStr) {
      stmp = Integer.toHexString(b & 0xFF);
      if (stmp.length() == 1) {
        // 如果是0至F的单位字符串，则添加0
        out.append("0").append(stmp);
      } else {
        out.append(stmp);
      }
    }
    return out.toString();
  }

  private static byte[] hex2byte(byte[] b) {
    int size = 2;
    if ((b.length % size) != 0) {
      throw new IllegalArgumentException("长度不是偶数");
    }
    byte[] b2 = new byte[b.length / 2];
    for (int n = 0; n < b.length; n += size) {
      String item = new String(b, n, 2);
      b2[n / 2] = (byte) Integer.parseInt(item, 16);
    }
    return b2;
  }
}
